There is an ever-increasing need for air filtering systems that can be rapidly deployed to protect an enclosure against noxious airborne agents released in the vicinity of the enclosure. Every year there are numerous incidents of noxious fumes entering buildings and causing illness and disruptions due to accidents, deliberate attacks or malicious pranks.
There currently is heightened concern about super-toxic airborne agents being released as part of a chemical, biological or radiological (“CBR”) attack launched by terrorists in or near a metropolitan area, a residential area, office complex, governmental buildings, medical facilities, or other public or private buildings or areas. In addition, military personnel in combat areas may need protection from releases of airborne CBR agents in the vicinity of a tent or other enclosure area where the troops are bivouacked or have set up a field command or field hospital, and so forth.
There is a need and demand for portable filter units capable of protecting a room airspace or other enclosure airspace against nuclear, biological, and chemical agent attacks that occur outside the enclosure, as well as capturing any internal contamination within a negative pressure area prior to release to the outside air. In this regard, easily portable CBR filter units are needed that can be conveniently handled, transported, and rapidly deployed into service without requiring time-consuming or complicated installation steps or infrastructure or support. CBR filter units can be expected to be potentially deployed in a wide variety of different CBR threat scenarios requiring a highly versatile unit.
Portable air cleaning units for use in the nuclear industry have been described that have a fan assembly that is integrally connected always on the downstream side of a filter assembly, such that the air cleaning unit is structurally designed and capable of only being operated in an air draw-through mode relative to the filter assembly. A filter unit of that type is described in the Nuclear Air Cleaning Handbook, DOE-HDBK-XXXX-2002, U.S. Dept. of Energy, Chapter 6, Jun. 28, 2002 (“Draft”), pp. 216–220. That filter configuration, however, would have serious drawbacks if implemented as a general airspace cleaner used to clean and pressurize an enclosure when this unit is located in the contaminated area. Although not recognized or address in the prior art, in that general airspace cleaning scenario, air leakage or infiltration would occur, or would be at high risk of occurring, in the intervening air passage or at the associated air seals that structurally must be made between the filtering and fan assemblies or around filter service doors panels that are required of such a filter unit. Air infiltration into that filter unit could occur when the fan assembly is being used to draw or pull air through the filter unit due to contaminated air present in the surrounding airspace bypassing the filter assembly by infiltrating through the air sealed connection or duct between the filter and fan assemblies. In this manner, contaminated unfiltered air can get sucked into and combine with the filtered air stream. In that undesired infiltration situation, the actual or potential problem is that filtered air can become recontaminated by the contaminated infiltrating air before it is discharged from the filter unit. The prior art does not mention or address this application or problems arising therein. If an attempt were made to design the leakage or infiltration problem away, i.e., attempt to manufacture a bona fide completely air-tight filter unit enclosure, that generally would be too costly for filter units intended for wide market distribution including private consumers.
The present invention recognizes, addresses and solves the above-mentioned needs and problems relative to portable CBR filter systems.